What do you expect to get out of it? If you want an overview of how a Game Engine and Game is made and architected from Scratch, you can start from the beginning now, and you should be able to follow through with a decent understanding of what goes into it.
If you want to use this to learn C, you could, but it will be tough. If you want to program with Casey, you will be able to pick up his style, and kinda better follow what he is doing as well as picking up a good feel for the language. But practicing and experimenting outside of the videos will be key to actual understanding, as with anything.
The series is targeted at those who already know C/C++, but he did give a weeks intro to C on Windows for the first week, so with your python knowledge, you should be able to stay with him. His C week is intended for those that already know a c like language, such as Python, Java or JavaScript.